The Skull


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The eight cranial bones of the skull are shown.  The mandible is the lower jaw bone.  The maxilla is superior to the mandible, comprising the upper lip and side of the nasal region.  The nasal bone is anterior.  The lacrimal surrounds the eye socket.  The ethmoid is anterior to the lacrimal.  The frontal bone is large, and takes up the forehead region.  The zygomatic is lateral to the eye socket, and the sphenoid is just behind it.  The temporal bone makes up much of the side of the skull.  The parietal is large, taking up much of the top and rear portions of the skull.  The occipital bone makes up the lower back of the skull.
The bones of the skull support the structures of the face and protect the brain. (credit: modification of work by Mariana Ruiz Villareal)

OpenStax Biology 2e

The bones of the skull support the structures of the face and protect the brain. The skull consists of 22 bones, which are divided into two categories: cranial bones and facial bones. The cranial bones are eight bones that form the cranial cavity, which encloses the brain and serves as an attachment site for the muscles of the head and neck. The eight cranial bones are the frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, and the ethmoid bone. Although the bones developed separately in the embryo and fetus, in the adult, they are tightly fused with connective tissue and adjoining bones do not move.

The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. The auditory ossicles consist of three bones each: the malleus, incus, and stapes. These are the smallest bones in the body and are unique to mammals.

Fourteen facial bones form the face, provide cavities for the sense organs (eyes, mouth, and nose), protect the entrances to the digestive and respiratory tracts, and serve as attachment points for facial muscles. The 14 facial bones are the nasal bones, the maxillary bones, zygomatic bones, palatine, vomer, lacrimal bones, the inferior nasal conchae, and the mandible. All of these bones occur in pairs except for the mandible and the vomer.

Illustration shows a front-end view of a skull. The frontal bone is the prominent bone that makes up most of the top of the skull. The parietal bone sphenoid bones make up the side of the skull. Two nasal bones make up the bridge of the nose. The zygomatic bone is the cheek bone. The vomer is a single bone in the middle of the nose. The maxilla makes up the upper jaw, and the mandible is the lower jaw. The lacrimal is a bone on the inner center of they eye. The nasal conchae are bones inside the nose.
The cranial bones, including the frontal, parietal, and sphenoid bones, cover the top of the head. The facial bones of the skull form the face and provide cavities for the eyes, nose, and mouth. Source: OpenStax Biology 2e

Although it is not found in the skull, the hyoid bone is considered a component of the axial skeleton. The hyoid bone lies below the mandible in the front of the neck. It acts as a movable base for the tongue and is connected to muscles of the jaw, larynx, and tongue. The mandible articulates with the base of the skull. The mandible controls the opening to the airway and gut. In animals with teeth, the mandible brings the surfaces of the teeth in contact with the maxillary teeth.


Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: